The Motion Severity Index is a statistical measure of Helideck motion designed to improve on traditional Heave Pitch and Roll and to provide a common framework for use across both UK and Norwegian sectors of the North Sea. The MSI is function of the ratio of horizontal (lateral and longitudinal) to vertical accelerations of the Helideck. Accurate Helideck motion measuring equipment measures this parameter continuously and a statistical program within the Muir Matheson PACE software is used to predict the most likely maximum value that should occur in the next 20-minute period, based on measurements in a 20-minute moving window. This statistical value is the MSI.

The Wind Severity Index is the equivalent statistical measure of the Wind Speed. Taken together the WSI and MSI provide aviators with a clear, comparative measure of Helideck stability and offer the basis for an empirical safety landing limit. The major helicopter manufacturers are able to set those limits according to helicopter type.

Muir Matheson provide equipment meeting this specification and have the ability and experience to meet the challenging sensor mounting requirements set by the regulatory authorities.


  • Tel: 01224 791222
  • Fax: 01224 791555



  • Muir Matheson Limited
  • Aberlan House
  • Woodburn Road
  • Blackburn Industrial Estate
  • Aberdeen
  • AB21 0RX
  • United Kingdom
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Registration Details

  • Registered in Scotland No. SC182820
  • VAT Registered No. GB 716 9914 03
  • Registered Office: Aberlan House